Oil tanning



Patented Aug. 10, 1926.

UNITED STATES,

PATENT OFFICE.

ALLEN ROGERS AND BISHAN NARIAN MATHUR, F B ROOKLYN,' NEW YORK.

OIL TANNING.

No Drawing.

This invention relates to oil tanning; and

- it comprises a method of converting skins or hides into leather of the character of chamois, crown, etc., wherein the skin is milled and otherwise treated with a soapy composition of pasty nature containing water and alkali-containing saponified products derived from oils, this composition being most advantageously made from'marine 1" annual oil; all as more fullyhereinafter set forth and as claimed. In the usual routine of operation, in making leather from skins by the oil tanning or samian process skins are placed in stocks, oil added and the skins milled, usually for about four hours. They are then piled down and again milled and so on until the oil is well absorbed when the skins are placed in a warm room to dryout the waterand complete the tanning, being thereafter pressed to remove the excess of oil, washed in a sodium carbonate solution, dried, staked and buffed. 5 The whole operation takes about ten days.

It is the object of the present invention to provide a method of producing this class of leather, economizin time and giving a better product. To t is end, instead'of using oil, as in the ordinary method of operation,

we employ a saponified product derived from such oils with the aid of alkali. All of these oils contain glycerids of unsaturated fatty acids of oily nature "whose exact character is not very well known. Probably acids of the oleic series C H O and 0 ,11, 0 are always present although oils from difl'erent'sources are, technically different. Whilev other oils maybe used we find it most advantageous for the present purposes to employ marine animal oils of the type of cod oil, shark liver oil and seal oil and make soaps therefrom in a special way. While we do not wish to limit ourselves to anytheory it is believed that in this operation of making soap the unsaturated portion of the molecular group of the fatty acid in the oil readily becomes hydroxylated; giving eventually bodies which unite-with the hide substance. And apparently upon the dparticular structure of the unsaturated aci s depends much of the final result. At all eventswhile. tanning may be obtained in greater or lessdegree oils from other; sources, marine animal oils give the best results. Soaps suitable for occurrence of any excess of alkali.

leather.

by the use of soapy-products made from Application filed August 31, 1925. Serial No. 53,719..

solution being somewhat less than that necessary to saponify all the oil. Potash may be used in lieu of soda but is not better. An alkaline composition is, not desired in the present process and it is safer to leave the soap with some unchanged oil to avoid Baum caustic soda solution is a desirable strength. Under the influence of heat and in the presence of the water of the mixture,

the unsaturated groups of the fatty acids of the oil apparently become eventually hydroxylated; giving solutions having a strong aflinity for the amino substances of hide. Free acids made from these soaps have a tanning action but are not so efficient as the soaps and are not as convenient to use.

The pasty water-containing mass of soaps made in the way just described, or in any other suitable manner, without removal of,

the water, is used in oil tanning in lieu of the customary oil, the physical operations performed and the succession of steps-being otherwise essentially the same.

Using the soapy material it is only necessary to mill the skins therewith for three or four hours, hang up to dry, or pack down over night, .cmill for two hours the next day and hang up to dry in a warm room. Under some circumstances inone stage of opera- .tion we may use some oil in addition to the soaps. When the skins are dried tannage is complete and nothing more is needed than the washing and drying to give a finished The process works quicker at around 100' F. than at ordinary temperature; but drying at room temperature may be used. Producing leather in this manner the whole operation can be completed in three or four days, which includes washing,

staking and buifing.

the present process may be made by placing into a soap crutcher or kettle 60 pohnds of A charge of suitable soapy material" for seal oil, shark liver or cod liver oil and heat.-

ing to 170 'F. Towthe warm, oil is added a cool solution of 6 pounds of commercial caustic soda in 35 pounds of water. The mixture of oil and lye isstirred until smooth and is then dumped into a container for cooling. When cooled the product is if smooth paste of the consis en y of lard; this paste containing the original water, some glyeerine, soaps of the unsaturated and saturated acids of the oil and a little unchanged oil. The amount of soda used is about sutficient to give a 75 per cent saponification; that is to leave about per cent of unchanged oil. The foregoing is given merely as a good way of producing desirable material for the present purposes. Other ratios of oil and caustic soda may he used; and the temperature varied,,hut on the whole we find that a 75 per cent saponification gives the best result. \Vhile other oils may be eniployed,.they do not give as good results. \Vhere other oils, such as menhaden, whale or even linseed or olive oils are to be used,

. it is better to use them in admixture with at least some of the marine animal oils specified. ()f the marine animal oils we find that on the whole the best results are given by cod liver, shark liver oils and seal oils.

.In using a composition made as described, the skins or hides are lnilled with it in stocks or mills for about two hours, using about half a gallon of the paste for each dozen average skins. Aft'er milling for two hours one-fourth gallon or more of the paste is introduced and millingresumed, usually for about two hours. placed in piles or hung over night in a moderately warm room and the next day milled again for two hours, after which onefourth gallon or more of the paste is added The skins may then be with the resumption of milling for twohours more or until the compound is well absorbed. \Vhen the material is sufiiciently worked into the skins they are hung up in a warm loft and allowed to dry slowly, the temperature of the drying room being, advantageously, between 110 and 120 F. A closed room gives the best results. After drying the skins are washed in warm water,

say 100 F. The water may contain a small amount of soda ash. After washing the skins are again dried, milled to soften them and finally buffed.

The foregoing directions are, of course, merely given as exemplificatory. The amount of compound required of course varies with the size of the skin. As a rule, however, we use about 50 per cent of compound onthe pickled weight of the hides or skins. The described method may be combined with the usual methods of oil tanning. For example in a modified form of our invention, the soapy compound is used for a preliminary treatmentand the hides or skins are then treated with straight oil or a mixture of compound and oil. In so doing the weakening efi'ect of straight oil is obviated and more stretch is secured.

Leather produced in this'manner does not get hard when used for washing automobiles and has more strength and body than the usual chamois skin. It can be used for many other purposes and we regard the present process as applicable in the manufacture of chamois, crown leather, buff leather, glove leather, etc. It can also be applied with advantage in the treatment of furs during the leathering operation.

' While not desiring to limit ourselves to anytheory in the matter it is our present impression that unsaturated fatty acids, and particularly thoseoccurring in marine animal oils become hydroxylated at the point of double bond; the point at which there is a double union between carbon atoms. Such a double union characterizes these unsaturated acids. And it is our present belief that the hydroxylated group enters into I chemical union with ammo groups in the hide substance. Certainly in the present process there is not an oxidation of the type which is supposed to characterize the reactions in the usual processes of oil tannage.

However, as stated, we do not limit ourselves to any theory but desire to claim merely the method of producing the results we secure; viz, tanning of skins and furs with asoapy paste made by reaction of caustic alkali on oils; and particularly marine animal oils.

What we claim is z- Y 1. .A process of producing so-called oil tannage of furs and skins wherein tanning is effected with an alkali-containing soapy composition of pasty nature containing an ezrlcess of oil and made from marine animal 01 s.

2. A process of producing so-called oil tannage of furs and skins wherein tanning K is effected by water-containing soapy material, such soapy material containing alkali saponified products of marine animal oils and unchanged oil and being'olf pasty nature.

- 3. In the manufacture ofoil tanned furs, skins and hides, the process which comprises sap'onlifying marine animal oils with an amount of caustic alkali solution sufficient to saponify part but not all of the oil and working the pasty product thereby produced into the material to be tanned.

4. A process of producing so-called oil tannage of furs andskins wherein a preliminary tanning is effected in a soapy product made from marine animal oil, and containing an excess of oil and completing the tanning by oil tanning.

5. A process of producin so-called oil tannage of furs and skins w erein tanning is eflected with a pasty mixture of oil and of soap made'from a marine animal oil and alkali.

In testimony whereof, we have hereunto aflixed our signatures, this 29 day of August, 

